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LM3409: Does driving EN low turn off PFET?

Brian Kaplan
Prodigy 10 points
Part Number: LM3409

As the title suggests, I'd like some clarification regarding the EN pin of the LM3409. I'm using the IC for a constant current source that needs to be selectively enabled/disabled via a digital pin from a microcontroller. If I drive the EN pin low, will this also turn off the PFET? The load and supply will remain connected to the circuit at all times. Is the LM3409 capable of disconnecting the load from the supply on its own or will I need additional circuitry?

Thanks,

Brian

  • 0
    TI__Mastermind 28655 points

    Hello Brian,

    Yes it will turn the driver off, PFET open, you do not need additional circuitry.  Also not that it will go into low power mode when VCC discharges below the VCC  UVLO threshold (section 8.4.1, page 18 of the datasheet), this will cause a slight delay to return back to the on-state since VCC has to recharge when enabled.  If this is not desired UVLO can be pulled low to disable the output.

    Best Regards,